The intraocular delivery of ionizing radiation for the treatment of age-related macular degeneration (“AMD”) is disclosed in deJuan et al. U.S. Pat. No. 6,875,165, which is incorporated herein by reference. Methods and apparatus for intraocular brachytherapy are disclosed in U.S. Ser. No. 11/559,958, filed Nov. 15, 2006 (2007/0118010), U.S. Ser. No. 11/056,763, filed Feb. 11, 2005 (2005/0277802), U.S. Ser. Nos. 11/228,030, filed Sep. 15, 2005 (2006/0111605), and 11/593,683, filed Nov. 7, 2006 (2007/0055089), which are also incorporated herein by reference. These applications generally disclose a handheld radiation delivery device that houses a radiation source wire (“RSW”). The device includes a cannula adapted to receive the RSW when in the treatment position, and to be inserted into the interior of an eye to deliver ionizing radiation (preferably beta radiation) to a target tissue. The present application is directed to an advanced radiation delivery system suitable for use in the treatment of diseases of the eye, such as AMD, as well as other diseases.